The present invention relates to liquid crystal display cells, and more particularly to liquid crystal display cells constructed with an improved seal for the fill opening thereof.
Liquid crystal display cells presently known in the art are generally constructed of a pair of spaced apart glass plates having transparent electrodes on the facing surfaces thereof. The plates are bonded together by a seal material about the periphery of the plates to define an inward volume adapted to confine a thin film of liquid crystal material which, when selectively addressed by voltages applied to the transparent electrodes, varies between light transmissive and opaque states to define a display image.
In manufacturing such cells it is usual to construct a closed cell containing the liquid crystal material. In the manufacturing process, this can be accomplished by forming a relatively small opening, preferably in the seal, for filling the cell with liquid crystal material. Upon completion of the fill operation, various types of plugs have been utilized to close the cell.
Sealing of the cell is a critical step in manufacture, since most known liquid crystal materials are highly susceptible to attack by various contaminants. Some contaminants are derived from the atmosphere and gain entry to the cell at the time of manufacture, or possibly later by permeating the seal of the cell. Other contaminants can originate in the seal material itself.
However, it is believed that a major cause of contamination in presently known liquid crystal cells is interaction between the liquid crystal material and the material utilized to seal the fill opening. One effect of contamination in the cell is to cause deterioration of the function or performance of the cell and thereby to reduce its useful life as a display.